Florida Responds to Cold Weather Bleaching

Left: A diver from The Nature Conservancy observes a recently dead coral head at an Upper Keys inshore patch reef. Right: This transplanted staghorn colony was unable to withstand the severe cold temperatures. Photo credit: The Nature Conservancy

Florida Keys National Marine Sanctuary (FKNMS) management and biologists are assessing the damaged and dead corals left behind after water temperatures dipped to record lows. Coral bleaching often occurs when water temperatures get too hot, but life-threatening stress and bleaching also occur when water temperatures drop too low. Some Florida Keys and South Florida water temperatures fell below 60 degrees–the lethal threshold for corals–during an historic 12-day cold snap at the start of the new year. Temperatures registered 52 degrees in some nearshore areas of the Florida Keys National Marine Sanctuary. Coral reefs farther offshore appear to be less severely impacted. Wintery waters in Florida also killed manatees and untold numbers of fish.

The cold-bleached and dead corals were reported by scientists working as part of a NOAA stimulus grant coral reef restoration project. Consequently, for a two-week period, January 25 through February 5, a disturbance response monitoring team will be surveying sites from the Dry Tortugas through Martin County to assess and monitor changes in coral health and die off. By launching the assessment immediately, divers will be able to collect valuable scientific clues, such as species identification and determine cause-of-death, before algae overtakes the dead corals, making such investigation impossible. Coral reef managers and scientists are optimistic that this rare event may give a better understanding of reef resilience and help determine which corals bounce back after stress, which will improve future conservation efforts. The last time such a cold water bleaching event happened in Florida was the winter of 1977-78.